Anatomical repair of nerve membranes in crushed mammalian spinal cord withpolyethylene glycol

Acute damage to axons is manifested as a breach in their membranes, ion exc hange across the compromised region, local depolarization, and sometimes co nduction block. This condition can worsen leading to axotomy. Using a novel recording chamber, we demonstrate immediate arrest of this process by appl ication of polyethylene glycol (PEG) to a severe compression of guinea pig spinal cord. Variable magnitudes of compound actions potentials (CAPs) were rapidly restored in 100% of the PEG-treated spinal cords. Using a dye excl usion test, in which horseradish peroxidase is imbibed by damaged axons, we have shown that the physiological recovery produced by polyethylene glycol was associated with sealing of compromised axolemmas. Injured axons readil y imbibe horseradish peroxidase-but not following sealing of their membrane s. The density of nerve fibers taking up the marker is significantly reduce d following polyethylene glycol treatment compared to a control group. We f urther show that all axons-independent of their caliber-are equally suscept ible to the compression injury and equally susceptible to polyethylene glyc ol mediated repair. Thus, polyethylene glycol-induced reversal of permeabil ization by rapid membrane sealing is likely the basis for physiological rec overy in crushed spinal cords. We discuss the clinical importance of these findings.